Why doesn't this individual do the trade themselves and gets someone else to do it?
You know a lot of exchanges give a good discount to large buyers (on fees) ...
Because the money is in physical cash and the individual is trying to take advantage of a tax loophole in their country that prevents the cash from being able to be deposited in their bank account directly. It has to be a direct exchange cash for BTC otherwise they won't be able to take advantage of the loophole